class ListNode{
    public int val;
    public ListNode prev;
    public ListNode next;
    public ListNode(int val){
        this.val=val;
    }
}
public class MyLinkedList {
    public ListNode head;
    public ListNode last;


    public void display(){
        ListNode cur=head;
        while(cur!=null){
            System.out.print(cur.val+" ");
            cur=cur.next;
        }
        System.out.println();
    }

    public int size(){
        ListNode cur=head;
        int count=0;
        while(cur!=null){
            count++;
            cur=cur.next;
        }
        return count;
    }

    public boolean contains(int key){
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                return true;
            }
        }
        return false;
    }

    //头插法
    public void addFirst(int data){
        ListNode node=new ListNode(data);
        if(head==null){
            head=node;
            last=node;
        }else{
            node.next=head;
            head.prev=node;
            head=node;
        }
    }

    //尾插法
    public void addLast(int data){
        ListNode node=new ListNode(data);
        if(head==null){
            head=node;
            last=node;
        }else{
            last.next=node;
            node.prev=last;
            last=node;
        }
    }


    public ListNode searchIndex(int index){
        ListNode cur=head;
        while(index!=0){
            cur=cur.next;
            index--;
        }
        return cur;
    }
    //任意位置插入，第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if(index<0||index>size()){
            System.out.println("index位置不合法");
            return ;
        }
        if(index==0){
            addFirst(data);
            return ;
        }
        if(index==size()){
            addLast(data);
            return ;
        }
        ListNode node=new ListNode(data);
        ListNode cur=searchIndex(index);
        node.next=cur;
        cur.prev=node;
        node.prev=cur.prev;
        cur.prev.next=node;
    }


    public void remove(int key){
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                if(cur==head){
                    head=head.next;
                    if(head!=null){
                        head.prev=null;
                    }else{
                        last=null;
                    }
                }else{
                    cur.prev.next=cur.next;
                    if(cur.next!=null){
                        cur.next.prev=cur.prev;
                    }else{
                        last=last.prev;
                    }
                }
                return;
            }else{
                cur=cur.next;
            }
        }
    }

    public void removeAllKey(int key){
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                if(cur==head){
                    head=head.next;
                    if(head!=null){
                        head.prev=null;
                    }else{
                        last=null;
                    }
                }else{
                    cur.prev.next=cur.next;
                    if(cur.next!=null){
                        cur.next.prev=cur.prev;
                    }else{
                        last=last.prev;
                    }
                }
                //return;
            }else{
                cur=cur.next;
            }
        }
    }

    public void clear(){
        ListNode cur=head;
        while(cur!=null){
            ListNode curNext=cur.next;
            cur.prev=null;
            cur.next=null;
            cur=curNext;
        }
        head=null;
        last=null;
    }




    public static void main(String[] args) {
        MyLinkedList myLinkedList=new MyLinkedList();
        myLinkedList.addFirst(2);
        myLinkedList.addFirst(3);
        myLinkedList.addFirst(4);
        myLinkedList.addIndex(3,333 );
        myLinkedList.addIndex(2,3);
        myLinkedList.remove(4);
        myLinkedList.display();
    }
}
